GRPCK(8)                  (02/07/2020)                   GRPCK(8)

     NAME
          grpck - verify integrity of group files

     SYNOPSIS
          grpck [options] [group [ shadow ]]

     DESCRIPTION
          The grpck command verifies the integrity of the groups
          information. It checks that all entries in /etc/group and
          /etc/gshadow have the proper format and contain valid data.
          The user is prompted to delete entries that are improperly
          formatted or which have other uncorrectable errors.

          Checks are made to verify that each entry has:

          +o   the correct number of fields

          +o   a unique and valid group name

          +o   a valid group identifier (/etc/group only)

          +o   a valid list of members and administrators

          +o   a corresponding entry in the /etc/gshadow file
              (respectively /etc/group for the gshadow checks)

          The checks for correct number of fields and unique group
          name are fatal. If an entry has the wrong number of fields,
          the user will be prompted to delete the entire line. If the
          user does not answer affirmatively, all further checks are
          bypassed. An entry with a duplicated group name is prompted
          for deletion, but the remaining checks will still be made.
          All other errors are warnings and the user is encouraged to
          run the groupmod command to correct the error.

          The commands which operate on the /etc/group and
          /etc/gshadow files are not able to alter corrupted or
          duplicated entries.  grpck should be used in those
          circumstances to remove the offending entries.

     OPTIONS
          The -r and -s options cannot be combined.

          The options which apply to the grpck command are:

          -h, --help
              Display help message and exit.

          -r, --read-only
              Execute the grpck command in read-only mode. This causes

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              all questions regarding changes to be answered no
              without user intervention.

          -R, --root CHROOT_DIR
              Apply changes in the CHROOT_DIR directory and use the
              configuration files from the CHROOT_DIR directory.

          -s, --sort
              Sort entries in /etc/group and /etc/gshadow by GID.

          By default, grpck operates on /etc/group and /etc/gshadow.
          The user may select alternate files with the group and
          shadow parameters.

     CONFIGURATION
          The following configuration variables in /etc/login.defs
          change the behavior of this tool:

          MAX_MEMBERS_PER_GROUP (number)
              Maximum members per group entry. When the maximum is
              reached, a new group entry (line) is started in
              /etc/group (with the same name, same password, and same
              GID).

              The default value is 0, meaning that there are no limits
              in the number of members in a group.

              This feature (split group) permits to limit the length
              of lines in the group file. This is useful to make sure
              that lines for NIS groups are not larger than 1024
              characters.

              If you need to enforce such limit, you can use 25.

              Note: split groups may not be supported by all tools
              (even in the Shadow toolsuite). You should not use this
              variable unless you really need it.

     FILES
          /etc/group
              Group account information.

          /etc/gshadow
              Secure group account information.

          /etc/passwd
              User account information.

     EXIT VALUES
          The grpck command exits with the following values:

          0

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              success

          1
              invalid command syntax

          2
              one or more bad group entries

          3
              can't open group files

          4
              can't lock group files

          5
              can't update group files

     SEE ALSO
          group(5), groupmod(8), gshadow(5), passwd(5), pwck(8),
          shadow(5).

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